Osteomyelitis commonly occurs as a complication of bone surgery, open fracture, diabetic foot ulcer, penetrating wound, or similar condition. When superimposed upon one of these processes osteomyelitis is a difficult clinical problem which routine radiographic and the more sensitive nuclear medicine techniques often fail to diagnose. The lack of a sensitive and specific diagnostic tool can cause an unnecessary delay in the institution of proper therapy or the institution of unnecessarily aggressive and expensive therapy. We and others have utilized a variety of diagnostic algorithms with radioactive compounds and radiolabeled white blood cells to aid in the diagnosis of complicating osteomyelitis. Several methods exist for isolating white blood cells which differ considerably in the complexity of cell separation and the final cell purity. At least five different lipid-soluble Indium chelates have been used to label the cells. We propose to use four different labeled white cell preparations along with Indium-111 chloride alone to study a well documented canine model of osteomyelitis. This study will allow us to: 1) Determine the sensitivity and specificity of each of these agents during the progression of osteomyelitis from the acute to chronic stage. 2) Compare image quality both subjectively and objectively for each preparation. 3) Assess the usefulness of Indium-111 chloride alone as an imaging agent for osteomyelitis. 4) Choose the best cell type(s) to be isolated and labeled to diagnose each stage of osteomyelitis. 5) Determine the effect of antibiotic therapy on the ability of these agents to diagnose osteomyelitis and/or its resolution. Finally, this study will provide insight into the mechanism(s) of Indium-111 localizaation. By analyzing the distribution of radioactivity in the circulating blood cellular components and in the plasma, we hope to determine the in vivo stability of the Indium-111 labeled cells and the (bio)chemical form of any non-cellbound activity. The results of this study should allow one to select the optimum Indium-111 agent for the diagnosis of the stages of osteomyelitis. If limited to only one of these radiopharmaceuticals, one will better understand the advantages and limitations of that agent. A better understanding of the mechanisms of localization of the present "state-of-the-art" agents may aid in the future development of more effective radiopharmaceuticals for the detection of osteomyelitis.